Reaction of polyureas and formaldehyde and hydrolysis, and the products



REACTION F PQLYUREAS AND FORMALDE- HYDE AND HYDROLYSIS, AND THE PRGD-UCTS No Drawing. Application Gctober 7, 1.952, Serial No. 313,606

12 Claims. (Cl. 260--69) This invention relates to synthetic linearpolyurcas and more particularly to a new process for preparing fiberstherefrom.

This application is a continuation-in-part of our copcnding applicationSerial No. 197,501, filed November 24, 1950, now abandoned.

Linear condensation polyureas have been prepared from dibasic diaminesand carbonic acid or amide-forming derivatives thereof, e. g., theanhydridc, i. e., carbon dioxide; however, certain of these polyureas,although readily prep-arable by the polyamide forming reactions taughtin U. S. Patents 2,071,250, 2,071,251, 2,071,253, 2,130,948, have beenof little utility because of the extreme difficulty experienced informing shaped objects from them. For instance, no convenient or readilyfeasible method for preparing fibers therefrom by Wet spinningprocedures is known. Similarly, the very high softening points of thesepolyureas have militated against melt spinning them by the standardprocedures used with the other linear fibenforming polyamides, e. g.,polyhexamethyleneadiparnide and the like. These difficulties areparticularly apparent in the case of the polyureas containingpolymethylene chains separating the urea units and most particularlywith polyureas of this type wherein the polymethylene chains arerelatively short. For instance, polyethylene, polytrimethylene,polytetra methylene, and polyhexarnethylene polyureas show no tendencyto melt but rather decompose at extremely high temperatures. it hasproven possible to plasticize polyhexarnethylene urea with certainpolyhydroxy aromatic hydrocarbons, e. g., m-cresol, and in such aplasticized condition to melt-spin the polyurea. However, such aprocedure is obviously not readily amenable to standard commercialprocedures.

This invention has as an object a method for preparing shaped objects,particularly fibers, from these polyureas. A particular. object is amethod for preparing shaped objects, and particularly fibers, frompolyureas from the short chain polymethylenediamines, e. g.,tetramethyleneand hexamethylenediamines, the relatively high thermalresistivity of which polyureas would suggest their use in many highquality outlets demanding the utmost in fiber properties, particularlyas regards insensitivity to heat as is desired, for instance, in tirecords. Another object is the preparation of tough, strong, markedly heatresistant shaped objects from high molecular weight polyureas, i. e.,high molecular weight condensation polyamides from diarnines andcarbonic acid or the amide-forming derivatives thereof. Other objectswill appear hereinafter.

These objects are accomplished by the present invention wherein a highmolecular weight linear polyurea condensation product, of inherentviscosity of at least 0.7 in solution in 98% sulfuric acid at aconcentration atent of 0.5 gm. per cc. of solution wherein at least 50%on a molar basis of the combined urea units carry hydrogen on both ureanitrogens, i. e., are --NHCONH- units, is reacted in solution in asolvent predominately, i. e., in major proportion, a strongoxygen-containing acid whose dissociation content is greater than 1 10-with from 0.2 to 1.0 mole of formaldehyde for each mole weight of saidcombined urea unit carrying hydrogen on both urea nitrogeus, i. e., foreach said --NHCONH- unit, forming the reaction mixture thus obtainedinto the desired shaped objects, e. g., films or fibers, by wet spinningor wet casting into an aqueous coagulating medium, and finallyhydrclyzing the thus formed formaldehyde modified polyurea in diluteaqueous mineral acid, preferably at elevated temperatures, until thecombined formaldehyde is substantially removed, i. e., until thestarting polyurea is substantially completely regenerated in the desiredshaped form. Because of the greater ease of handleability in theformation of shaped objects therefrom, it is preferred to use from 0.2to 0.6, and most preferably from 0.3 to 0.5, mole of formaldehyde foreach mole weight of combined -NHCONH- unit When the polyurea has no morethan four chain atoms between each -NHCONH- unit and with from 0.2 to1.0, and most preferably from 0.5 to 1.0, mole of formaldehyde for eachmole Weight of combined -NHCONH- unit when the polyurea has more thanfour chain atoms between each -NHCONI-l-unit. The process of thisinvention is especially useful in the formation of fibers.

The following examples, in which the parts given are by weight, aresubmitted to further illustrate and not to limit this invention. As usedtherein, inherent viscosnty (mm) is defined by the following equation:

W7 1 viral wherein In is the natural logarithm,

I solution '61:. 7 solvent EXAMPLE I A solution is prepared bydissolving 64.5 parts of N,N-polyhexamethyleneurea (prepared fromhexamethylenediamine and diethyl hexamethylenediurethane in the mannergiven in U. S. Patent 2,181,663 and of inherent viscosity 0.99) in 605parts of 98% formic acid and 54.5 parts of sulfuric acid (95.5% minimumconcentration) and 29.5 parts of 37% formaldehyde (10.9 parts offormaldehyde on a 100% basis, corresponding to 0.8 mole of formaldehydeper urea unit, i. e., per -NHCONH unit). The clear, viscous solutionthus obtained is pressure spun at the rate of 2.9 ml. of spinningsolution per minute through a 30 hole (0.005 inch hole diameter)stainless steel spinneret into water at 50 C. The yarn travel in thecoagulating bath is 38 inches and the yarn windup on a Godet wheel is at20 feet per minute. The yarn is then drawn 4.621 through water at 100 C.immediately after coming off the Godot wheel and taken up on a windupbobbin. The yarn is then boiled taut on the windup bobbin in 2% aqueoussulfuric acid for two hours and finally water washed to remove traces ofacid, dried, sized, and twisted two turns per inch. The resulting yarn,after boil-off for 45 minutes in skein form, exhibited the followingproperties:

Denier 96.0 Dry tenacity/elongation (g. p. d./per cent) 1.7/18 Wettenacity/elongation (g. p. d./per cent) 1.4/18 Modulus dry (g. p.d./100%) 31 Modulus wet (g. p. d./100%) 19 Sticking point 230 C. Percent shrinkage in 100 C. water before boiloif 3 1 As measured on theInstron tensile tester.

EXAMPLE 11 Part A.-ln a stainless steel bomb of internal capacitycorresponding to 1,000 parts of water is placed 40 parts of purified,freshly distilled tetramethylenediamine in an open end glass vessel-thelatter being used to prevent contact of the diamine with the internalsurface of the metal bomb. The bomb is closed, purged of air bypressuring to the top pressure of a standard commercial fifty poundcylinder of. carbon dioxide and then bleeding to a pressure of 25lbs/sq. in. and repeating the pressuring and bleeding cycle for threetimes at room temperature. [This top pressure will vary from 600 to1,000 lbs./ sq. in. depending on the ambient temperature and the amountof carbon dioxide in the cylinder.] The bomb is then pressured to 500lbs/sq. in. with carbon dioxide and then heatedto 190 C. The pressure isthen adjusted to the maximum cylinder pressure available, approximately1,000 lbs/sq. in., and heating is continued at 190 C. for a total of twohours. The temperature is then raised to 200 C. and subsequently to 210C. and held at each of these temperatures for two hours. The temperatureis then raised to 235 C. and the vessel then bled to a pressure of 225lbs/sq. in. and then repressured to full carbon dioxide cylinderpressure. This procedure is repeated every 30 minutes for a total periodof two hours. The temperature isthen raised to 250 C. and the vesselbled and repressured as at 235 C. for a period of two more hours,followed by the same bleeding and repressuring schedule at a temperatureof 265 C. for a period of two more hours. The temperature is finallyraised to 280 C. andmaintained at this level for a period of four hourswhile bleeding and repressuring as before. The bomb is then cooled, bledto atmospheric pressure, opened and the solid N,N-polytetramethyleneureacake removed from the glass liner, cut into pieces weighingapproximately 0.5 gram each and then heated at 306 C. under a pressurecorresponding to approximately that of 2 mm. of mercury for four hours.There is thus obtained 36 parts of N,N-polytetramethyleneurea as awhite, hard polymer, which exhibits at 25 C. an inherent viscosity insulfuric acid of 1.07 at a concentration of 0.5 g. of polymer per 100cc. of solution.

Part B.A solution is prepared. by dissolving 13.9 parts of the polyureafrom tetramethylenediamine and carbon dioxide (prepared in general asdescribed previ ously. and of inherent viscosity 1.2) in 100 parts of amixture of 80.4% formic acid and 19.6% sulfuric acid (6:1 by volume). Tothe resulting solution is added 1.46 parts of formaldehyde, introducedas 37% formalin (sufficient to furnish 0.4 mole of CHzO per unit of thepolyarnide). The clear, viscous solution is spun in general as describedpreviously in Example I into a 20% aqueous sodium sulfate bath at 50 C.and the yarn drawn 5.811 through but aqueous sulfuric acid solutionbetween the Godet wheel and the windup bobbin. The yarn on the windupbobbin is then boiled taut for two hours in 2% or 5% aqueous sulfuricacid' and subsequently washed free of acid with water, dried 4 andtreated as before. the following properties:

Samples of this yarn exhibited Percent Shrinkage 100 0. water 1 1 PartC.Another solution prepared in a similar fashion to that previouslydescribed is spun under the same conditions except that the bath traveldistance is 100 inches. The yarn is drawn 1.4:1 through air in beingtaken off the Godet wheel to a windup bobbin. This air-drawn yarn iswashed and dried and then drawn through hot oil at 2l0-220 C. at drawratios of :1 and 5.711. These hot drawn yarns are boiled off taut on thebobbin in 3% aqueous sulfuric acid for two hours, then skeined andboiled off in water. These yarns exhibit the following properties:

Hot-draw ratio 5. 0:1 5. 0:1 5. 7:1 Denier 73. 3 94. 0 82. 3

Dry tenacity/elongation (g. p. (EL/percent,

Incline Plane) 5/18 5. 0/32 4. 3/19 Percent Shrinkage at C 2. 0 4. 1 1.8Modulus (g. p. d./100 percent) 47 l Sticking point C... 300 o.

wherein X is the divalent radical joining the urea nitrogens in thestarting polyurea. In the final acid hydrolysis step such ringstructures are hydrolyzed with the regeneration of the original linearpolyurea.

Solutions of these uron intermediates, i. e., the formaldehyde/polyureareaction products, in strong acids, preferably oxygen-containing strongacids, are surprisingly stable for as long as 24 hours or more at 30 C.in contrast to the formation of insoluble, infusible crosslinkedpolyarnides from such reaction mixtures prepared from the long-chain,dibasic acid/diamine condensation polyamides. Fibers and films may beformed from these solutions at room or elevated temperatures as high as40 C. without any evidence of deposition of insoluble crosslinkedproducts. Higher solution temperatures are generally avoided because ofexcessive bubbling, particularly when formic acid is used.

The polyureas to which the filmand fiber-forming process of thisinvention can be applied, as has been stated before, are the linearcondensation polymers resulting from the interaction under amide-formingconditions of essentially equimolar portions of carbonic acid or any ofits amide-forming reactants with dibasic amines, i. e., diamines.Carbonic acid or any of its amide-forming reactants such as the acidhalides, the anhydride, the esters, for instance with phenols or thelower alkanols, the half amide, i. e., carbamic acid, the half amideesters, i. e., the urethanes, and diisocyanates (see U. S. Patent2,292,243) can be used in conjunction with the desired diamine inpreparing the polyureas. However, for reasons of readier availability,lower cost and easier handling in the polymerization reaction, it ispreferred to use carbonic acid anhydride, i. e., carbon dioxide.

The diamines, which are used in conjunction with carbonic acid or itsamide-forming derivatives to form the polyureas which are usable in theprocess of this invention, are those which contain two hydrogencontaining amino groups and are free from nuclear hydrogen, i. e.,hydrogen on nuclear (aromatic) carbon, activated by strong ortho-,para-directing groups. Such groups may be defined as those possessing apolarizing force of less than about 0.40 l dynes as discussed in somedetail at pages 13 through 31 or" Mechanisms of Reactions atCarbon-Carbon Double Bonds, Price, Interscience, 1946. Included amongsuch groups as indicated in the table on page 25, ibid., are the amino,methoxy, dimethylarnino, chloro, methyl, and chloromethyl radicals butnot aminomethyl. Expressed another Way, since the amino group is sostrongly ortho-, paradirecting, this means that those amines wherein oneor both or the amino groups is or are directly bonded to nuclear carbonmust have substituents on the carbons orthoand parato said amino groups,i. e., carrying no hydrogens on said carbons. To illustratespecifically, diaminodurene or p-xylylenediamine can be used inpreparing polyureas usable in the process of this invention, althoughthe latter are not as acid resistant as is desired. On the other handthe diaminobenzenes or even the aminomethylanilines cannot be used inpreparing operable polyureas. The reason for this, of course, resides inthe well-known aniline/formaldehyde resin forming reaction. Polyureascontaining these activated hydrogens would obviously react through suchhydrogens with the formaldehyde used in the process of this invention toform cross-linked, un' handleable, and probably unregenerable products.

Since the process of this invention depends upon the reaction of thepolyureas with formaldehyde and the concomitant formation thereby ofpolyurons, the polyureas used must contain combined urea chain unitscarrying hydrogen on each urea nitrogen, i. e., must contain NHCONH-units as obtained from diprimary diamines. In this connection, it shouldbe pointed out that polyureas prepared from mixtures of diprimarydiamines and disecondary diamines containing less than 50% disecondarydiamine are usable in the process of this invention. Such mixedpolyureas contain a preponderance of hydrogen-bearing urea nitrogens, i.e., are prepared from mixtures of diprimary diamines and disecondarydiamines which are predominantly primary. Examples of the preferredprimary diamines include, linear, saturated, aliphatic primary diamines,e. g., tetra-, penta-, hexa-, hepta octa-, and decamethylenediamines;branched chain, saturated, aliphatic primary diamines, e. g.,3-methylhexamethylenediamine; aromatic primary diamines, wherein theamino groups are directly bonded to an aromatic nucleus and theremaining hydrogens of the annular aromatic carbons are replaced bylower aliphatic hydrocarbon radicals, e. g., diarninodurene, i. e.,l,4-diamino-2,3, 5,6-tet=ramethylbenzenc; aromatic/21.1% phatic primarydiamines, wherein the amino groups are separated from the aromaticnucleus by a chain of at least one and preferably two aliphatic carbons,e. g., 1,4-di-(beta-aminoethyl)benzene; cycloaliphatic primary diamines,e. g., 1,4-diaminocyclohexane; aliphatic cycloaliphatic primarydiamines, e. g., l,4-diaminomethylcyclohexane,bis-(4-aminocyclohexyl)methane; primary diamines containing aheteroatom, e. g., oxygen, nitrogen, or sulfur, in the chain or radicalseparating the two amine groups, e. g., l,7-diamino-4-oxaheptane,l,7-diamino-4- thiaheptane, l,7-diamino-4-methyl-4-azaheptane, and bis-(B-aminopropoxy) ethane.

Because of the greater ease of formation or the poly ureas therefrom inhigher molecular weights, it is pre ferred to use those diamines whereinthe amino nitrogens are directly bonded to aliphatic carbons.Particularly preferred among this group are those diamines which otherthan the amino nitrogens are solely non-aromatic, i. e., aliphatic,including cycloaliphatic, hydrocarbon, i. e., diamines which apart fromamino nitrogen and hydrogen thereon are saturated hydrocarbon, i. e.,saturated aliphatic and cycloaliphatic hydrocarbon. Due to the decreasedformation of colored by-products and the greater ease of polymerizationto higher molecular weight polymers, as well as their greateravailability at lower cost, the primary diamines wherein the two primaryamino groups are separated by a straight chain hydrocarbon raical, i.e., the polymethylenediamines, are especially preferred.

in carrying out the process of this invention, formaldehyde from anysource can be used. For instance, the formaldehyde can be added as suchin its anhydrous form, usually as the solid cyclic trimer,alpha-trioxymethylene or meta-formaldehyde, or it can be added in itsnormal commercial form as a 37 to 40% aqueous solution, i. e., theso-called formalin. Alternatively, the formaldehyde can be formed insitu, e. g., through reaction between cyclic formals and aqueous acid.The amount of formaldehyde used in carrying out the process of thisinvention varies with the polyurea. It is within the scope of thisinvention to react from 10% to 50 of the urea groups bearing hydrogen oneach urea nitrogen in the polyureas with formaldehyde and to carry outthe spinning process on the intermediate polyurons therefrom re sulting.For most eh'icient formation of fibers by the process of this invention,it has been found that at least of the -NHCONH- groups in the startingpoly-- urea must be reacted with formaldehyde to form the polyurons. Themost effective level of formaldehyde reaction is a direct function ofthe nature of the polyurea being used. For instance, tough, strong, heatresistant fibers can be most readily prepared from anN,N-polytetrainethyleneurea by reacting from 15 to of the urea groupswith formaldehyde, wet spinning into fibers, and subsequently drawingand regenerating the polyurea. On the other hand, the best fibers areprepared from an MN'-polyhexamethyleneurea by reacting from 25 to 50% ofthe urea groups with formaldehyde, wet spinning, acid regenerating, etc.In general, the best products are obtained from the various polyureas byreacting from 15 to 50% of the --NHCONH groups in the polyurea withformaldehyde.

The polyurea at a concentration of 10-20% in the strong acid, e. g.,sulfuric, formic, perchloric, benzene sullonic, p-toluenesulfonic,methanesulfonic, ethanesulfouic, chlorosulionie, methylsulfuric, etc.acids, is reacted with the formaldehyde until the viscosity which atfirst increases due to the addition of the formaldehyde returns tosubstantially the initial value. It is to be noted that the formaldehydein the desired amount is normally added at once to the solution of thepolyurea and that the viscosity of the solution increases markedly uponthe addition out as the reaction proceeds returns to substantially theinitial value.

The aqueous coagulating medium used in preparing films and fibers fromthese formaldehyde/polyurea reaction products can contain the watersoluble salts of ammonia and alkali metal or alkaline earth metals,preferably with the strong mineral acids, and in any case the aqueouscoagulating medium is preferably at slightly elevated temperature, e.g., 70 C. In some instances,

' water alone serves sufficiently Well as a coagulating medium; whereasin others, relatively high concentrations as high as by weight of thealkali metal or alkaline earth metal salts are needed. The necessity ofusing these salts in the coagulating baths and the concentration foundmost efiicient are both functions of the density of the polyureas beingspun. Preferably the density of the coagulating bath is maintained atthat point at which the yarn being spun will move easily through thecoagulating bath to the take-up wheel without adhering to itself orfalling to the bottom of the coagulating bath. The density of thepolyurea yarn being spun varies with the degree of polymerization, i.e., the molecular weight of the polyurea, and also to an appreciableextent on the carbon content of the diamine used iii-preparing thepolyurea. The controlling factor appears to be the number of carbonscontained in the diamine for each of the amino nitrogens. For instanceas illustrated in the examples, the polyurea from hcxamethylenediaminecan be readily and easily spun into a warm water coagulating bath;whereas, for greatest ease in handling as well as the quality of yarntherefrom obtained, the polyurea from tetramethylenediamine ispreferably spun into an aqueous coagulating bath containingapproximately 20% of one of these alkali metal or alkaline earth metalmineral acid salts, e. g., sodium sulfate.

The polyurea fibers of this invention can be prepared in oriented, i.e., drawn, fashion. This can be accomplished by carrying out the drawingat either or both of tWo stages in the process. For instance, the fiberscan be drawn at that stage in the process where they are first formed,i. e., as first removed from the coagulating bath. At this stage thefibers are presumably those of the intermediate polyuron. Drawing atthis stage may be in the range from 1.4:1 to 10:1 and may be done ineither one step or in several steps, for example, one draw of 3:1followed by a second draw of 2:1. Drawing may also be carried out on theformaldehyde modified yarns after they have been washed substantiallyfree of acid (and any residual salts from the coagulating bath, if anyare used) and dried. it; is usually desirable and in many instances evennecessary that drawing of the washed and dried formaldehyde modifiedpolyurea yarns be carried out at elevated temperatures, for instance, inthe range 150 to 250 C., usually using an inert heat transfer medium, e.g., mineral oil, to more readily effect the heating of the yarn. Drawingmay also be accomplished in a hydrolyzing medium, e. g., hot 5% sulfuricacid, as shown in the examples. In any event, no matter how the draw isapplied, whether in two stages or in one, whether as first formed orafter being washed free of acid and dried, Whether in a heat transfermedium or a hydrolyzing medium at elevated temperatures, it is advisablethat a total draw of from 2:1 to 8:1 and preferably from 4 to 6:1 beeffected. Yarns drawn to the intermediate ratios generally exhibittenacity-elongation characteristics more desirable for most purposesthan those drawn to lower or higher ratios.

The regeneration of the drawn formaldehyde modified polyurea yarns iscarried out by simply immersing the yarn, usually in packages or, moreconveniently, on bobbins, i. e., as obtained directly from the spinningprocess, in an aqueous mineral acid solution at 25 to 100 C. for fromone to six hours or even longer at temperatures near room temperature.if desired, of course, the regeneration process can be accomplished in acontinuous fashion by passing the yarn, drawn or not, as obtained fromthe spinning process directly through an aqueous mineral acid bath. Inthis latter instance, it is usually preferred to use high temperaturesand thereby cut down the operating time necessary to complete theregeneration. For the most desirable strength properties in theregenerated polyurea yarn, it is preferred that at least 80% of thecombined formaldehyde be removed by the hydrolysis procedure. Expressedanother way, this means that the preferred yarns will have less than 10%of the original NHCONH- linkages in the previously described uron rings.

In carrying out the last stage of the process of this invention, i. e.,the regeneration of the starting polyurea by dilute aqueous acidhydrolysis of the intermediate polyuron fibers, it is necessary tohydrolyze a major proportion of the uron rings, i. e., to remove a majorproportion of the combined formaldehyde. As the degree of hydrolysisincreases, i. e., as the percentage of removal of the combinedformaldehyde increases, the fibers be- 55 come stronger, tougher, morewaterdnsensitive, more heat-resistant, and less elastic. formaldehyde isremoved, until but about 0.15% of'the urea groups are in the form ofuronlgroups, i. e., when the starting polyurea has all but about 0.15%of its urea groups regenerated, the fibers of this invention areoutstandingly stronger, tougher, and more thermally resistant. Thesepreferred products have all but about 0.3% of the combined NHCONH groupsregenerated, i. e., have but about 0.3% of the combined NHCONH units inthe form of uron rings, i. e., those fibers containing but about 0.6mole percent formaldehyde calculated on a molar basis of the NHCONHunits present, which can be no less than 50% of the units in thepolymer. of the extremely high levels of water insensitivity exhibitedby the polyurea/polyuron copolymers when this.

low level of uron content, i. e., this high level of --NHCONHregeneration, is attained, it is extremely difficult to carry thehydrolysis further, i. e., to remove more of the combined formaldehydeand complete the regeneration of the -NHCONH- units.

This regeneration step, i. e., hydrolysis of the intermediate uronrings, i. e., removal of the combinedformaldehydc, can be carried out inany aqueous acidic medium at temperatures in the range to 100 C. forfrom one to siX hours or more, depending on the temperature employed.Because of their greater hydrolytic efficiency, readier availability andlow cost, the dilute,

e. g., 0.25% to 10%, preferably 1-l0%, aqueous mineral;

acids, e. g., hydrochloric, sulfuric, nitric, phosphoric and the like,are preferred. Since the hydrolysis reaction is essentially completewith no polymer degradation and because of the convenience of suchconditions, his pre-- ferred to carry out the hydrolysis in the diluteaqueous mineral acids, e. g., 25% sulfuric acid for from one to threehours at the boil.

As stated previously, the first spinning stage of the process of thisinvention involves wet spinning a strong acid solution of theformaldehyde-modified polyurea into an aqueous coagulating bath,preferably at slightly elevated temperatures, usually in the range to 70C. Thus, the fibers are, at least for a short time, subjected to theaction of an aqueous strong acid. Despite this fact, the percentage ofcombined formaldehyde in the fibers obtained at this stage of theprocess is, within analytical errors, the same as that in the spinningsolution. At the end of this stage, the fibers are. still those.

of the formaldehyde modified polyurea, i. e., the polyurea/polyuron.Similarly with films, these new polymeric shaped objects have recurringurea groups, separated by aliphatic hydrocarbon chains, in whichpolymers from 0.10 to of the urea groups are in the form of uron,

groups. the recurring units wherein R is a divalent saturated aliphatichydrocarbon radical and R is hydrogen or a monovalent hydrocarbon Whenthe combined It is to be noted that because- The polymers may beformulated as having radical. The polyuron polymers having from 0.15 to10%, or better, 0.15 to 2.5%, of the recurring urea -NOON I groups inthe form of uron,

groups are preferred because of the strength, toughness, etc., of theshaped objects therefrom.

Thus, to prepare the desired polyurea fibers, the final stage of theprocess is necessary, i. e., the dilute aqueous acidic hydrolysis atelevated temperatures in the neighborhood of 100 C. This finalregeneration stage of the starting polyurea in fiber form can apparentlyonly be carried out by this dilute aqueous acidic hydrolysis at elevatedtemperatures. It cannot be carried out by merely boiling with water forthe same amount of time nor by heating the formaldehyde treated yarn atthe same temperature under vacuum for the same amount of time.

Thus, 100 parts of polytetramethyleneurea ('77lnh. 1.2) is dissolved in700 parts of a 14.3/85.'7% by volume concentration of sulfuric/ 100%formic acid solution, 28.5 parts of 37% formaldehyde, corresponding to10.5 parts of formaldehyde (20% of the theoretical amount needed toreact with all the urea links in the polyurea) is added, and theresultant modified polyurea formed into fibers by wet spinning into anaqueous coagulating bath containing 20% of sodium sulfate at 50 C. Theyarn so formed is stretched 1.4:1 in air after being taken up from theGodet wheel. Samples of the yarn so formed are (a) washed with coldwater and air dried, (b) taken directly from the take-up bobbin whilestill wet with aqueous coagulating bath (which, of course, becomes moreacid as the spinning proceeds) and placed in boiling water for two hoursand subsequently air dried, (c) taken directly from the take-up bobbinwhile still wet and placed in an oven at 100 C. for two hours under avacuum corresponding to 2 mm. of mercury, (d) washed in water and driedin an oven for two hours at 100 C. under the same vacuum as above, and(e) washed in water and dried. These various samples were analyzed forcombined formaldehyde by a colorimetric procedure involving chromotropicacid. The samples indicated the following formaldehyde contents,respectively, 10.0%, 9.92%, 9.48%, 9.59%, 9.62%.

The theoretical value for the combined formaldehyde in the startingformaldehyde modified polyurea, i. e., a polytetramethyleneurea having20% of the urea links reacted with formaldehyde, is 9.8%. Thus, it canbe seen that the formaldehyde modified polyurea contains the requiredamount of combined formaldehyde after the spinning process (a) when ithas been merely washed with cold water, (1;) when it has been boiledwith water for two hours (said water containing the residual strong acidadsorbed on the fibers from the spinning process), (c) when it has beenheated at 100 C. for two hours under vacuum in the presence of theadsorbed acid, and (d) when it has been washed free of the adsorbed acidand again heated at 100 C. for two hours under vacuum. These resultsdemonstrate the necessity of the dilute aqueous acidic hydrolysis stepin preparing, i. e., regenerating, the desired polyureas.

The polyurea shaped objects, as prepared by the process of thisinvention, are useful in the regular fields of use for such objects. Forinstance, the polyurea fibers are useful in preparing fabrics for useper se or for reinforcing rubber articles such as tires and the like.The polyurea films are useful as wrapping materials, fabric replacementitems and the like. The polyurea films and fibers are particularlyoutstanding in their various fields of use because of their relativelygreater thermal remo est sistivity. This makes the polyurea fibers ofparticular interest in such uses as tire cord.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed for obvious modifications will occur to those skilled in theart.

What is claimed is:

1. A process for the preparation of shaped objects having at least onedimension large with respect to another which comprises reacting, insolution in a strong, oxygen-containing acid of ionization constant ofat least l l0 a high molecular weight linear polyurea having at least50% combined intrachain -NHCONH- units, of inherent viscosity of atleast 0.7 in 98% sulfuric acid at a concentration of 0.5 gm. per 100 cc.of solution, and free of hydrogen on aromatic carbon activated by astrong ortho-, para-directing group, with, as essentially the solereactant for the polyurea, from 0.2 to 1.0 mole of formaldehyde for eachmole weight of combined -l*IHCONH- group, forming the reaction mixturethus obtained into the desired shape, coagulating the same, and finallyhydrolyzing the thus formed formaldehyde modified polyrner by bringingthe same in contact with dilute aqueous mineral acid until at least ofthe combined formaldehyde is eliminated but at least 0.15 of the ureagroups remain in the form of uron groups.

2. A process for the preparation of shaped objects which comprisesreacting, in solution in strong, oxygencontaining acid of ionizationconstant of at least 1 l0 a high molecular weight linear condensationpolymer of carbonic acid and a saturated acyclic aliphatic diprimarydiamine of up to four carbons, said polymer being of inherent viscosity,in solution in 98% sulfuric acid at a concentration of 0.5 gm. per 100cc. of solution, of at least 0.7, with from 0.2 to 0.6 mole offormaldehyde for each mole weight of combined -NHCONH- in the polyurea,forming the reaction mixture thus obtained into the desired shape,coagulating the same, and finally hydrolyzing the thus formedformaldehyde modified polymer by bringing the same in contact withdilute aqueous mineral acid until at least of the combined formaldehydeis eliminated but at least 0.15% of the urea groups remain in the formof uron groups.

3. A process for the preparation of shaped objects which comprisesreacting, in solution in strong, oxygencontaining acid of ionizationconstant of at least l 10' a high molecular weight linear condensationpolymer of carbonic acid and a saturated acyclic aliphatic diprimarydiamine of up to four carbons, said polymer being of inherent viscosity,in solution in 98% sulfuric acid at a concentration of 0.5 gm. per 100cc. of solution, of at least 0.7, with from 0.3 to 0.5 mole offormaldehyde for each mole weight of combined NHCONH- in the polyurea,forming the reaction mixture thus obtained into the desired shape,coagulating the same, and finally hydrolyzing the thus formedformaldehyde modified polymer by bringing the same in contact withdilute aqueous mineral acid until at least 95% of the combinedformaldehyde is eliminated but at least 0.15% of the urea groups remainin the form of uron groups.

4. A process for the preparation of shaped objects r which comprisesreacting, in solution in strong, oxygencontaining acid of ionizationconstant of at least 1 10 a high molecular weight linear condensationpolymer of carbonic acid and tetramethylene diamiue, said polymer beingof inherent viscosity, in solution in 98% sulfuric acid at aconcentration of 0.5 gm. per 100 cc. of solution, of at least 0.7, withfrom 0.3 to 0.5 mole of formaldehyde for each mole weight of combined-NHCONH-in the polyurea, forming the reaction mixture thus obtained intothe desired shape, coagulating the same, and finally hydnolyzing thethus formed formaldehyde modified polymer by bringing the same incontact with dilute aqueous mineral acid until at least 95% of thecombined formaldehyde is eliminated but at least 0.15% of the ureagroups remain in the form of uron groups.

5. A process for the preparation of shaped objects which comprisesreacting, in solution in strong, oxygencontaining acid of ionizationconstant of at least 1 1O a high molecular weight linear condensationpolymer of carbonic acid and a diamine composition consistingessentially of diamines free from hydrogen on nuclear (aromatic) carbon,of more than four chain carbons, and having hydrogen on amino nitrogenwhich composition contains a major proportion of diprimary diamines,said polymer being of inherent viscosity, in

solution in 98% sulfuric acid at a concentration of 0.5 gm. per 100 cc.of solution, of at least 0.7, with, as essentially the sole reactant forthe polyurea, from 0.2 to 1.0 mole of formaldehyde for each mole weightof combined -NHCONH in the polyurea, forming the reaction mixture thusobtained into the desired shape, coagulating the same, and finallyhydrolyzing the thus formed formaldehyde modified polymer by bringingthe same in contact with dilute aqueous mineral acid until at least 95%of the combined formaldehyde is eliminated but at least 0.15 of the ureagroups remain in the form ofuron groups.

6. A process for the preparation of shaped objects which comprisesreacting, in solution in a strong, oxygencontaining acid of ionizationconstant of at least 1 1O a high molecular weight linear polyurea, ofinherent viscosity, in solution in 98% sulfuric acid at a concentrationof 0.5 gm. per 100 cc. of solution, of at least 0.7, having hydrogen onat least 50% of the urea nitrogens and free of hydrogen on aromaticcarbon activated by a strong orthopara-directing group and having atleast four chain carbons between the urea groups with, as essentiallythe sole reactant for the polyurea, from 0.5 to 1.0 mole of formaldehydefor each mole weight of combined NHCONH- in the polyurea, forming thereaction mixture thus obtained into the desired shape, coagulating thesame, and finally hydrolyzing the thus formed formaldehyde modifiedpolymer by bringing the same in contact with dilute aqueous mineral aciduntil at least 95% of the combined formaldehyde is eliminated but atleast 0.15% of the urea groups remain in the form of uron groups.

7. A process for the preparation of shaped objects which comprisesreacting, in solution in a strong oxygencontaining acid of ionizationconstant of at least 1 21 high molecular weight linear condensationpolymer of carbonic acid and an aliphatic diprimary diamine of more thanfour chain carbons saturated hydrocarbon but for the two NH2 groups,said polymer being of inherent viscosity, in solution in 98% sulfuricacid at a concentration of 0.5 gm. per 1000 cc. of solution, of at least0.7, with from 0.5 to 1.0 mole of formaldehyde for each mole weight ofcombined NHCONH- in the polyurea, forming the reaction mixture thusobtained int the desired shape, coagulating the same, and finallyhydrolyzing the thus formed formaldehyde modified polymer by bringingthe same in contact with dilute aqueous mineral acid until at least 95%of the combined formaldehyde is eliminated but at least 0.15 of the ureagroups,

remain in the form of uron groups.

8. A shaped object of a high molecular weight linear condensationpolymer having recurring groups separated by saturated aliphatichydrocarbon chains wherein from about 0.10% to' 50% of said groups arein the form of uron,

groups, the extra chain valences of the remaining 1lIoo1' I- groups notsatisfied by hydrogen being satisfied by monovalent hydrocarbonradicals.

9. A shaped object of a high molecular weight linear condensationpolymer having recurring I TCOI I groups separated by saturatedaliphatic hydrocarbon chains where-in from about 0.15 to 10% of saidgroups, the extra chain valences of the remaining bIOO-h groups notsatisfied by hydrogen being satisfied by monovalent hydrocarbonradicals.

10. A shaped object of a high molecular weight linear condensationpolymer having recurring it-Conic groups separated by saturatedaliphatic hydrocarbon chains wherein from about 0.15 to 2.5% of saiddecode groups are in the form of uron,

NC 0N ('JHz-O-OH;

groups, the extra chain valences of the remaining -i s ool rgroups notsatisfied by hydrogen being satisfied by monovalent hydrocarbonradicals.

11. A shaped object of a high molecular weight linear condensationpolymer having recurring 1 I-oo1 I- groups separated by tetramethylene,

-CH2CH2CH2CH2- radicals wherein from about 0.15 to 1.0% of said 1 IC O1I groups are in the form of uron,

NGON

CH2-O-CH2 groups, the. extra chain valences of the remaining groups notsatisfied by hydrogen being satisfied by monovalent hydrocarbonradicals.

12. A shaped object of a high molecular weight linear condensationpolymer having recurring decentgroups separated by tetramethylene,

-CH2CH2CH2CH2- radicals wherein from about 0.15% to 2.5% of said.

deco-1'sgroups are in the form of uron,

groups are satisfied by hydrogen.

References Cited in the file of this patent UNITED STATES PATENTSCarothers Sept. 20, 1938 Cairns Feb. 5, 1946 14 Cairns -1 Nov. 18,Cairns May 4, Buckley et a1. May 1,

FOREIGN PATENTS Great Britain Jan. 18, Great Britain Nov. 19,

1. A PROCESS FOR THE PREPARATION OF SHAPED OBJECTS HAVING AT LEAST ONEDIMENSION LARGE WITH RESPECT TO ANOTHER WHICH COMPRISES REACTING, INSOLUTION IN A STRONG, OXYGEN-CONTAINING ACID OF IONIZATION CONSTANT OFAT LEAST 1X10-4, A HIGH MOLECULAR WEIGHT LINEAR POLYUREA HAVING AT LEAST50% COMBINED INTRACHAIN -NHCONHUNITS, OF INHERENT VISCOSITY OF AT LEAST0.7 IN 98% SULFURIC ACID AT A CONCENTRATION OF 0.5 GM. PER 100 CC. OFSOLUTION, AND FREE OF HYDROGEN ON AROMATIC CARBON ACTIVATED BY A STRONGORTHO-, PARA-DIRECTING GROUP, WITH, AS ESSENTIALLY THE SOLE REACTANT FORTHE POLYUREA, FROM 0.2 TO 1.0 MOLE OF FORMALDEHYDE FOR EACH MOLE WEIGHTOF COMBINED -NHCONH- GROUP, FORMING THE REACTION MIXTURE THUS OBTAINEDINTO THE DESIRED SHAPE, COAGULATING THE SAME, AND FINALLY HYDROLYZINGTHE THUS FORMED FORMALDEHYDE MODIFIED POLYMER BY BRINGING THE SAME INCONTACT WITH DILUTE AQUEOUS MINERAL ACID UNTIL AT LEAST 80% OF THECOMBINED FORMALDEHYDE IS ELIMINATED BUT AT LEAST 0.15% OF THE UREAGROUPS REMAIN IN THE FORM OF URON GROUPS.